Children who acquire Dutch as their first language show a strong preference for using infinitival verb forms during the early stages of grammatical development. This exemplifies the 'root infinitive' (RI) phenomenon, which has played a significant role in recent discussions on the development of syntax. Most accounts proposed thus far invoke an immaturity of the child's grammatical competence. We explore the possibility that the early predominance of infinitival forms is related to patterns in the language input. We analysed a corpus of utterances addressed by two Dutch-speaking mothers to their two- to three-year old sons. Root infinitive utterances amounted to 10%, and auxiliary-plus infinitive main verb constructions, which in terms of word order are maximally similar to RIs, constituted 30% of all verb-containing utterances. These figures render an account in terms of exposure to utterance structures unlikely. There is a moderate (but significant) correlation between frequency of occurrence of individual verb forms in the input and age of acquisition. However, infinitive verb forms are often acquired earlier than their input frequency would predict, and this may be related to an overall increased salience, due to their systematic appearance in sentence-final position and their relatively high conceptual transparency as compared to finite verbs.